The present invention concerns a fastening device comprising a male part and a female part selectively inserted into bores passing through a stack of at least two panels, these parts selectively cooperating with one another to mainstain the panels in a stack.
More precisely, the present invention concerns a fastening device comprising a male part and a female part selectively inserted into bores passing through a stack of at least two panels, these parts selectively cooperating with one another to maintain the panels in a stack, in which device the female part is an elastic clip formed by a cap extended by a hollow foot having different minimum and maximum internal transverse dimensions, in which the male part comprises a head extended by a barrel having at least a first given intermediate transverse dimension, between the minimum and maximum internal transverse dimensions, this barrel being selectively inserted into the hollow foot through an opening in the cap, and the hollow foot selectively adopting, as a function of at least one relative axial position of the barrel and the hollow foot, and for at least a first relative rotational position of the barrel and the foot, an unlocked configuration in which the foot has a reduced transverse dimension, and a locked configuration in which the foot is subjected by the barrel to a radial elastic expansion.
Devices of this type are described, for example, in the patent documents FR-2 464 396, GB-1 260 094 and GB-1 163 400.
In spite of the diversity of the structures that these documents of the prior art illustrate, the known devices do not make it possible to maintain a stack of panels without play, at least within a given range of thickness of this stack.
In this context, the object of the present invention is specifically to offer a device capable of solving this problem.
To this end, the device of the invention, which otherwise conforms to the generic definition given in the above preamble, is essentially characterized in that the cap is formed by a spring blade that is bent back on itself and that comprises at least one inner branch joined to the hollow foot and one outer branch into which the opening of the cap is pierced, and in that the inner and outer branches are apart from one another at least for the unlocked configuration of the hollow foot and are shaped so as to allow an elastic deformation of at least part of the outer branch when the foot moves from its unlocked configuration to its locked configuration.
In a preferred embodiment of the invention, the hollow foot comprises a plurality of prongs having respective attached ends by which these prongs are joined to the cap, and respective radially converging free ends, which between them define the minimum internal transverse dimension of the foot.
The male and female parts advantageously comprise at least first and second respective surface features disposed facing one another for an extreme relative axial position of the male and female parts, selectively obtained by completely inserting the barrel into the foot, the first and second surface features mutually cooperating to maintain the male and female parts in the extreme relative axial position.
The first surface feature can for example be formed by a radial protuberance of the barrel, such as a screw thread if the barrel is a threaded shaft, or a lug, and the second surface feature can be formed by the free ends of the prongs.
To increase the deformation of the foot between its unlocked configuration and its locked configuration, the first surface feature can advantageously be constituted by a lug disposed facing a corresponding hole in the foot, this lug passing through the hole when the foot is in both the unlocked configuration and the first rotational position relative to the barrel.
In an effective embodiment of the invention, the hollow foot comprises two prongs separated from one another by an open space for the unlocked configuration of the foot, and the barrel has at least a second transverse dimension that selectively enters the open space, the result of which is that the hollow foot selectively adopts its unlocked configuration for a second relative rotational position of the barrel and of the foot, independently from the relative axial position of the male and female parts.
For example, the barrel includes two smooth parts, each forming a flat surface running axially, these smooth parts making it possible to unscrew the fastening device by rotating the barrel relative to the foot.
In this case, the male and female parts advantageously comprise at least third and fourth respective surface features disposed facing one another for the locked configuration of the foot, these third and fourth surface features mutually cooperating to maintain the male and female parts in their first relative rotational position.
An elastic radial tab can be provided in the opening of the cap in order to selectively cooperate with the barrel and maintain it in a given axial position, or in a rotational position that determines either the locked or the unlocked configuration.
Furthermore, the inner branch of the cap preferably includes at least two internal elastic tabs capable of applying pressure to the stack of panels in the locked configuration of the foot.
The clip is advantageously formed by cutting, bending and heat treating a metal blank, for example made of tempered steel.
The third and fourth surface features can respectively be constituted by an axial rib of the barrel and a corresponding cutout of the cap, or by a recess of the head and a boss of the cap.
The barrel can also have a collar inserted into the opening of the cap counter to an elastic force and rendering the male and female parts inseparable from one another.
In order to obtain an elastic deformation of the outer branch, it is possible to provide for the head to press against this outer branch, for the locked configuration of the foot, and to move the inner and outer branches toward one another so as to generate an elastic stress between them.
However, it is also possible to provide for the head to pass through the outer branch and come to rest against the inner branch of the cap for the locked configuration of the foot.
In the latter case, which makes it possible to maintain stacks of various thicknesses without changing the diameter of the bores that pass through them, the male part can include a second head that remains outside the outer branch, even for the locked configuration of the foot, which facilitates the removal of the device.
The external surface of the hollow foot preferably corresponds to the shape of the bores provided in the stack of panels, the largest transverse dimension of the bore in the bottom panel itself being adapted to the thickness of the stack, particularly if the elastic deformation of the outer branch is obtained by means of a pressure exerted on this branch by the head.
Thus, the invention also concerns an assembly constituted by a fastening device as defined above in connection with this solution, and by a stack of panels or the like in which bores are provided, this assembly being such that:
the combined thickness of the panels is between 0.5 and 3 mm, while the largest transverse dimension of the bore in the bottom panel is 7.7 mm;
or the combined thickness of the panels is between 3 and 4.5 mm, while the largest transverse dimension of the bore in the bottom panel is 8.2 mm;
or the combined thickness of the panels is between 4.5 and 6 mm, while the largest transverse dimension of the bore in the bottom panel is 8.7 mm;
or the combined thickness of the panels is between 6 and 7 mm, while the largest transverse dimension of the bore in the bottom panel is 9.2 mm.